Symptoms of damage to the radial nerve and its branches

The radial nerve is formed from the posterior bundle of the brachial plexus and is the derivative of the ventral branches of the CV - CVIII of the spinal nerves. On the back wall of the axillary cavity the nerve descends downwards, being behind the axillary artery and being located successively on the abdomen of the scapular muscle and on the tendons of the latissimus muscle of the back and the large round muscle. Having reached the shoulder-arm angle between the inner part of the shoulder and the lower edge of the back wall of the axillary cavity, the radial nerve adjoins the dense connective tissue band formed by the connection of the lower edge of the latissimus muscle of the back and the posterior tendon part of the long head of the triceps muscle of the shoulder. Here is the place of possible, especially external, compression of the radial nerve. Further, the nerve lies directly on the humerus in the furrow of the radial nerve, otherwise called the spiral trough. This furrow is limited by the places of attachment to the bone of the outer and inner heads of the triceps arm muscle. This is how the channel of the radial nerve is formed, also called the spiral, brachial or cannabis channel. In it, a nerve describes a spiral around the humerus, passing from the inside and back in the anterior direction. The spiral canal is the second place of potential compression of the radial nerve. From it on the shoulder the branches approach the triceps brachii muscle and the elbow muscle. These muscles unbend the upper limb in the elbow joint.

The test for determining their sipa: the subject is offered to unbend a limb previously bent at the elbow joint; The examiner is resisting this movement and palpating the contracted muscle.

The radial nerve at the level of the outer edge of the shoulder at the border of the middle and lower third of the shoulder changes the direction of its course, turns ahead of the perforating external intermuscular septum, passing into the front compartment of the shoulder. Here the nerve is particularly vulnerable to compression. Below the nerve passes through the initial part of the humerus muscle: it is innervated by the long radius extensor of the hand and falls between it and the brachial muscle.

The humerus muscle (innervated by segment CV-CVII) flexes the upper limb in the elbow joint and penetrates the forearm from the supination position to the median position.

A test to determine its sipa: the subject is asked to bend the limb at the elbow joint and at the same time to penetrate the forearm from the supination position to the middle position between supination and pronation; The examiner is resisting this movement and palpating the contracted muscle.

The long radius extensor of the hand (innervated by the segment CV - CVII) unbends and retracts the brush.

Test to determine the strength of the muscle: suggest to unbend and withdraw the brush; The examiner is resisting this movement and palpating the contracted muscle. Passing the brachial muscle, the radial nerve crosses the capsule of the elbow joint and approaches the arch support. In the ulnar region at the level of the external epicondyle of the shoulder or several centimeters above or below it, the main trunk of the radial nerve is divided into a superficial and a deep branch. The superficial branch moves the subarchetral muscle to the forearm. In its upper third, the nerve is located outside of the radial artery and above the styloid process of the ray passes through the gap between the bone and the tendon of the brachial muscle on the back surface of the lower end of the forearm. Here, this branch is divided into five rear finger nerves (nn. Digitales dorsales). The latter branch out in the radial half of the dorsal surface of the hand from the nail phalanx I, the middle phalanx II, and the radial half of the third finger.

The deep branch of the radial nerve enters the gap between the superficial and deep bundles of the instep and is directed to the rear surface of the forearm. The dense fibrous upper edge of the superficial bundle of the instep is called the Froze arcade. Under the Froze arcade is also the place of the most probable occurrence of the tunnel syndrome of the radial nerve. Passing through the channel of the instep, this nerve is attached to the neck and the body of the radius and then exits to the back surface of the forearm, under the short and long surface extensors of the hand and fingers. Before going out to the rear of the forearm, this branch of the radial nerve supplies the following muscles.

1. The short radius extensor of the wrist (innervated by the segment CV-CVII) participates in the extension of the wrist.
2. The supinator (innervated by segment CV-CVIII) rotates and suppinates the forearm.

The test for determining the strength of this muscle: the researcher is suggested to supine the limb, which is bent in the elbow joint, from the position of pronation; the examiner is resisting this movement.

On the back surface of the forearm, a deep branch of the radial nerve innervates the following muscles.

The extensor of the fingers of the hand (innervated by the segment CV - CVIII) unbends the main phalanges of the II V fingers and simultaneously the brush.

Test to determine its strength: the subject is offered to unbend the main phalanges of the II-V fingers, when the middle and the nail are bent; the examiner is resisting this movement.

The elbow extensor of the hand (innervated by the segment CVI - CVIII) unbends and leads the brush.

A test to determine its strength: the subject is offered to unbend and bring the brush; The examiner is resisting this movement and palpating the contracted muscle. The extension of the deep branch of the radial nerve is the posterior interosseous nerve of the forearm. It passes between the extensors of the thumb to the wrist joint and sends twigs to the next muscle.

The long muscle that removes the thumb of the hand (innervated by the segment CVI - CVIII), allocates I finger.

Test to determine its strength: the subject is offered to withdraw and slightly unbend a finger; the examiner is resisting this movement.

The short extensor of the thumb (innervated by segment CVI-CVIII) unbends the main phalanx of finger I and withdraws it.

Test to determine its strength: the subject is offered to unbend the main phalanx of the first finger; The examiner is resisting this movement and palpating the strained tendon of the muscle.

The long extensor of the thumb (innervated by the segment CVII-C VIII) unbends the nail phalanx of the first finger.

Test to determine its strength: the subject is offered to unbend the nail phalanx of the first finger; The examiner is resisting this movement and palpating the strained tendon of the muscle.

The extensor of the index finger (innervated by segment CVII -CVIII) unbends the index finger.

Test to determine its strength: the subject is offered to unbend the II finger; the examiner is resisting this movement.

The extensor of the little finger (innervated by the segment CVI - CVII) unbends the V finger.

Test to determine its strength: the subject is offered to unbend V finger; the examiner is resisting this movement.

The posterior interosseous nerve of the forearm also delivers thin sensitive branches for the interosseous septum, the periosteum of the radial and ulnar bones, the posterior surface of the wrist and carpometacarpal joints.

The radial nerve is predominantly impellent and mainly supplies the muscles that extend the forearm, the hand, and the fingers.

To determine the level of damage to the radial nerve, one should know where and how the motor and sensitive branches leave it. The posterior cutaneous nerve of the shoulder branches into the area of the axillary outlet. It supplies the back surface of the shoulder almost to the elbow. The posterior cutaneous nerve of the forearm is separated from the main nerve trunk in the armpit angle or in the spiral canal. Regardless of the branch site, this branch always passes through the spiral canal, innervating the skin of the posterior surface of the forearm. The branches to the three heads of the triceps muscles of the arm extend in the region of the axillary fossa, the brachial axis and the spiral canal. The branches to the humerus muscle, as a rule, extend below the spiral canal and above the outer forearm of the shoulder. The branches to the long radial extensor of the wrist usually depart from the main nerve trunk, although below the branches to the previous muscle, but above the instep. The branches to the short radial extensor of the wrist may depart from the radial nerve, its superficial or deep branches, but it is also usually higher than the entrance to the duct of the instep. The nerves to the arch support can branch higher or at the level of this muscle. In any case, at least some of them pass through the cannula of the instep.

Consider the levels of damage to the radial nerve. At the level of the axillary angle, the radial nerve and the branches that branch away from it in the axillary fossa to the triceps muscle can be pressed down to the dense tendons of the latissimus muscle of the back and the large pectoral muscle in the tendon angle of the region of the axillary outlet. This angle is limited by the tendons of the two muscles and the long head of the triceps arm muscle. Here, external compression of the nerve can occur, for example, due to improper use of the crutch - the so-called "crutch" paralysis. The nerve can also be squeezed by the back of the chair at the clerical workers or by the edge of the operating table, over which the shoulder hangs during surgery. It is known to squeeze this nerve implanted under the skin of the chest by the driver of the heart rhythm. Internal compression of the nerve at this level occurs with fractures of the upper third of the shoulder. Symptoms of damage to the radial nerve at this level differ primarily by the presence of hypesthesia on the posterior surface of the shoulder, to a lesser extent - the weakness of extension of the forearm, as well as the absence or decrease of the reflex from the triceps muscle of the shoulder. When stretching the upper limbs forward to the horizontal line, a "hanging or falling brush" is revealed - a consequence of the brush extensions in the wrist and the II - V fingers in the metacarpophalangeal joints.

In addition, there is weakness of extension and retraction of the first finger. Can not and supination of the uncoupled upper limb, whereas with the preliminary flexion in the elbow joint supination due to the double-headed muscle is possible. Bending at the elbow of the perniovion of the upper limb is impossible due to paralysis of the brachial muscle. The hypotrophy of muscles of the dorsal surface of the shoulder and forearm can be detected. The hypoesthesia zone captures, in addition to the back surface of the shoulder and forearm, the outer half of the back surface of the hand and the 1st finger, as well as the main phalanx II and the radial half of the third finger. Compression damage of the radial nerve in the spiral canal is usually a consequence of fracture of the shoulder in the middle third. Nerve compression may occur shortly after fracture due to tissue edema and increased pressure in the canal. Later, the nerve suffers when it is squeezed by scar tissue or callus. With spiral canal syndrome, there is no hypoesthesia on the shoulder. As a rule, the triceps arm muscle does not suffer, since the branch to it is superficial - between the lateral and medial heads of this muscle - it is not directly attached to the bone. In this tunnel, the radial nerve is displaced along the long axis of the humerus during the period of contraction of the triceps muscle. The bone callus formed after a fracture of the shoulder can prevent such nerve movements during muscle contraction and thereby contribute to its friction and compression. This explains the occurrence of pain and paresthesia on the back surface of the upper limb when extending at the elbow joint against the action of the resistance force for 1 min with incomplete posttraumatic lesion of the radial nerve. Painful sensations can also be caused by finger compression during 1 min or by poking the nerve at the level of compression. In the rest, symptoms similar to those observed in the lesion of the radial nerve in the region of the armpit angle were detected.

At the level of the external intermuscular septum of the shoulder, the nerve is relatively fixed. This place is the most frequent and simple by the mechanism of compression lesion of the radial nerve. It is easily pressed against the outer edge of the radial bone during a deep sleep on a hard surface (gloss, bench), especially if the head presses the shoulder. Because of fatigue, and more often in a state of alcoholic intoxication, a person does not wake up in time, and the function of the radial nerve is turned off ("sleepy", paralysis, "paralysis of the garden bench"). With "sleep paralysis" there are always motor falls, but there is never a weakness of the triceps arm muscle, i.e. The paresis of extension of the forearm and the reduction of the reflex from the triceps muscle of the shoulder. In some patients, loss of not only motor functions but also sensitive ones can occur, but the zone of hypoesthesia does not extend to the posterior surface of the shoulder.

In the lower third of the shoulder above the outer supracondylum, the radial nerve is covered with the brachial muscle. Here, the nerve can also be squeezed in fractures of the lower third of the humerus or when the radial head is displaced.

Symptoms of damage to the radial nerve in the supranuminal region may be similar to "sleep paralysis." However, in the nervous case, there is no observed loss of motor functions without sensitive ones. The mechanisms of occurrence of these types of compression neuropathies are also different. The level of compression of the nerve is approximately the same as the place where the shoulder is pulled. In differential diagnostics, the definition of the upper level of provoking painful sensations on the back surface of the forearm and the hand is also helped with puncturing and finger compression along the projection of the nerve.

In some cases, it is possible to determine the compression of the radial nerve by the fibrous arch of the lateral head m. Triceps. The clinical picture corresponds to the above. Pain and numbness at the rear of the hand in the zone of supply of the radial nerve can periodically increase with intensive manual work, during long distance running, with sharp bending of the upper extremities in the elbow joint. In this case, the nerve is compressed between the humerus and the triceps muscle of the shoulder. Such patients are advised to pay attention when running at the angle of flexion in the elbow joint, to stop manual labor.

Quite often the cause of lesions of the deep branch of the radial nerve in the area of the elbow joint and upper arm of the forearm is the compression of its lipoma, fibroma. They usually manage to palpate. Removal of the tumor, as a rule, leads to recovery.

Among other causes of damage to the branches of the radial nerve, mention should be made of bursitis and synovitis of the elbow joint, especially in patients with rheumatoid polyarthritis, fracture of the proximal radial head, traumatic vascular aneurysm, professional overstrain with repetitive rotational movements of the forearm (conducting, etc.). Most often, the nerve is affected in the canal of the fascinator's fascia. Less often, it happens at the level of the elbow joint (from the place of passage of the radial nerve between the brachial and brachial muscles to the head of the radius and the long radial flexor of the wrist), which is designated as a radial tunnel syndrome. The cause of compression-ischemic nerve damage can be a fibrous tape in front of the head of the radius, dense sinewy edges of the short radius extensor of the wrist or Froze's arcade.

The instinctor's syndrome develops with a lesion of the posterior interosseous nerve in the area of the Froze arcade. It is characterized by nocturnal pains in the outer parts of the ulnar region, at the rear of the forearm, and, quite often, at the rear of the wrist and hand. Daytime pains usually occur during manual work. Particularly conducive to the appearance of pain, rotational movements of the forearm (supination and pronation). Often, patients note weakness in the hand, which appears during work. This can be accompanied by a violation of the coordination of movements of the hand and fingers. There is local soreness in palpation at a point 4 to 5 cm below the outer shoulder epicondyle in the groove radial to the long radius of the extensor carpus.

Use samples that cause or increase pain in the hand, for example, a supination test: both hands of the subject are tightly fixed on the table, the forearm is bent at an angle of 45 ° and is set at the maximum supination position; The examiner tries to translate the forearm into a position of pronation. This sample is performed for 1 minute, it is considered positive, if during this period pain occurs on the extensor side of the forearm.

Test extension of the middle finger: to cause pain in the hand can be a long (up to 1 minute) extension of the III finger with resistance to extension.

There is a weakness of supination of the forearm, extension of the main phalanges of the fingers, sometimes there is no extension in the metacarpophalangeal joints. A paresis of the lead of the 1st finger is also revealed, but the extension of the terminal phalanx of this finger is preserved. With the loss of the function of the short extensor and the long deflecting muscle of the thumb, it becomes impossible to radiate the brush in the plane of the palm. When the wrist is unbent, the wrist is diverted to the radial side due to loss of function of the elbow extensor of the wrist with the preservation of the long and short radius extensors of the wrist.

The posterior interosseous nerve can be squeezed at the level of the middle or lower part of the instep with a dense connective tissue. Unlike the "classic" instinctor instinct caused by compression of the nerve in the Froze arcade area, in the latter case, the symptom of finger compression is positive at the level of the upper and lower edges of the muscle. In addition, the paresis of the extension of the fingers with "lower instep" is not combined with the weakness of supination of the forearm.

Surface branches of the radial nerve at the level of the lower part of the forearm and wrist can be squeezed by a tight watch strap or handcuffs ("prisoner's paralysis"). However, the most common cause of nerve damage is the injury of the wrist area and the lower third of the forearm.

Compression of the superficial branch of the radial nerve with a fracture of the lower end of the radius is known as "Turner's syndrome," and the defeat of the branches of the radial nerve in the area of the anatomical snuff-box is called the radial tunnel syndrome of the wrist. Compression of this branch is a frequent complication of de Querven's disease (ligamentum I of the posterior carpal ligament). A short extensor and a long distal muscle of the first finger pass through this channel.

When the surface branch of the radial nerve is affected, patients often feel numbness on the back of the hand and fingers; Sometimes there is a burning pain on the back of the 1st finger. Pain can spread to the forearm and even to the shoulder. In the literature, this syndrome is called the Wartenberg paresis neuralgia. Sensitive abaissement is often confined to the path of hypoesthesia on the inner back of the first finger. Often, hypoesthesia can extend beyond the 1st finger to the proximal phalange of the 2nd finger and even to the rear of the main and middle phalanges of the 3rd and 4th fingers.

Sometimes the superficial branch of the radial nerve thickens in the region of the wrist. The finger compression of such a "pseudo-ambrosia" causes pain. The symptom of effleurage is also positive for effleurage along the radial nerve at the level of the anatomical snuffbox or the styloid process of the radius.

Differential diagnosis of the lesion of the radial nerve is carried out with the syndrome of the spinal root CVII, in which, in addition to the weakness of the extension of the forearm and the hand, the paresis of the reduction of the shoulder and flexion of the hand is revealed. If motor loss is absent, localization of pain should be considered. When the spine of CVII is affected, the pain is felt not only on the wrist, but also on the back surface of the forearm, which is not typical for the lesion of the radial nerve. In addition, radicular pain is provoked by movements of the head, sneezing, coughing.

For the syndromes of the level of the thoracic outlet, the emergence or intensification of pain in the hand when turning the head to a healthy side, as well as in the performance of some other specific tests, is characteristic. At the same time, the pulse on the radial artery can be reduced. It should also be borne in mind that if a part of the brachial plexus, corresponding to the root of CVII, is compressed at the level of the thoracic outlet, then a picture appears similar to that of the spine described above.

Electroneuromyography helps to determine the level of damage to the radial nerve. We can confine ourselves to research using needle-shaped electrodes of the triceps muscle of the shoulder, the brachial muscle, the extensor of the fingers, and the extensor of the index finger. In the instillation of the instep, the first two muscles will be retained, and in the latter two, during their complete voluntary relaxation, spontaneous (denervative) activity can be detected in the form of potentials of fibrillation and positive acute waves, and at the maximum arbitrary strain of muscles-the absence or shrinking of the potentials of the motor units. When the radial nerve is irritated on the shoulder, the amplitude of the muscular action potential from the extensor of the index finger is significantly lower than when the nerve is electrically stimulated below the supinator channel on the forearm. The determination of the level of damage to the radial nerve can also be helped by the study of latent periods-the timing of the nerve impulse and the rate of propagation of excitation along the nerve. To determine the rate of propagation of excitation For motor fibers of the nerve nerve, electrostimulation is carried out at various points. The highest level of irritation is the Botkin-Erba point, located several centimeters above the clavicle in the posterior triangle of the neck, between the posterior edge of the sternocleidomastoid muscle and the clavicle. Below, the radial nerve is irritated at the point of exit from the axillary fossa in the groove between the coracoid-brachial muscle and the posterior edge of the triceps brachial muscle, in the spiral trough at the mid-shoulder level, and also at the border between the lower and middle third arm where the nerve passes through the intermuscular septum, even distally - 5-6 cm above the outer supracondylum of the shoulder, at the level of the elbow (shoulder joint), at the rear of the forearm 8 to 10 cm above the wrist or 8 cm above the styloid process of the ray. Recording electrodes (concentric needle-shaped bowls) are inserted in the place of the maximal response to the stimulation of the nerve of the triceps muscle - the shoulder, the shoulder, the brachial, the extensor of the fingers, the extensor of the index finger, the long extensor of the thumb, the long abductor muscle or the short extensor of the thumb. Despite some differences in the points of stimulation of the nerve and the places of registration of the muscle response, the values of the rate of propagation of the excitation along the nerve are close to normal. Its lower limit for the "neck-armpit" section is 66.5 m / s. On a long stretch from the supraclavicular point of Botkin-Erba to the lower third of the shoulder, the average velocity is 68-76 m / s. In the area "axillary fossa - 6 cm above the outer shoulder epicondyle" the excitation propagation rate averages 69 m / s, and in the "6 cm above the outer shoulder epicondyle - forearm 8 cm above the styloid process of the ray" - 62 m / s at muscular potential from the extensor of the index finger. From this it is seen that the speed of propagation of excitation along motor fibers of the radial nerve on the shoulder is approximately 10% higher than on the forearm. Average values on the forearm - 58.4 m / s (fluctuations - from 45.4 to 82.5 m / s). Since the lesions of the radial nerve are usually one-sided, taking into account individual differences in the rate of propagation of excitation along the nerve, it is recommended to compare the indices on the diseased and healthy sides. Investigating the speed and timing of the nerve impulse from the neck to various muscles innervated by the first ray, we can differentiate the plexus pathology and the different levels of nerve damage. The lesions of the deep and superficial branches of the radial nerve differ easily. In the first case, only pain in the upper limb arises and motor movements can be detected, and the surface sensitivity is not disturbed.

In the second case, not only pain is felt, but paresthesia, there are no motor falls, but surface sensitivity is disturbed.

It is necessary to differentiate the compression of the superficial branch in the ulnar region from engaging it at the level of the wrist or lower third of the forearm. The zone of painful sensations and sensitive fallout may be the same. However, the test of an arbitrary forced extension of the wrist will be positive if the superficial branch is compressed only at the proximal level while passing through the short radius of the extensor carpus. It is also necessary to carry out tests with pinching or finger compression on the projection of the surface branch. The upper level, at which these effects are caused by paresthesia on the back of the hand and fingers, is the likely place of compression of this branch. Finally, the level of nerve damage can be determined by introducing 2-5 ml of a 1% solution of novocaine or 25 mg of hydrocortisone, which leads to a temporary cessation of pain and / or paresthesia. If the nerve blockade is performed below the site of its compression, the intensity of the painful sensations will not change. Naturally, you can temporarily relieve pain by blocking the nerve not only at the level of compression, but also above it. To distinguish the distal and proximal lesions of the superficial branch, first inject 5 ml of 1% solution of novocain at the border of the middle and lower third of the forearm at its outer edge. If the blockade is effective, it indicates a lower level of neuropathy. If there is no effect, repeated blockade is performed, but already in the elbow joint area, which relieves pain and indicates the upper level of the lesion of the superficial branch of the radial nerve.

Diagnosis of the site of compression of the superficial branch can also be helped by the study of the propagation of excitation through sensitive fibers of the radial nerve. The nerve impulse along them is completely or partially blocked at the level of compression of the surface branch. With partial blockade, the time and speed of propagation of excitation along sensitive nerve fibers are slowed down. Various research methods are used. With the orthodromy technique, excitation along sensitive fibers propagates toward the direction of the sensitive pulse. To do this, the irritating electrodes are positioned at the extremities more distally than the outgoing ones. With the antidromic technique, the propagation of excitation along the fibers in the opposite direction is fixed, from the center to the periphery. In this case, the electrodes proximally located on the extremity are used as irritants, and the distal electrodes are used as a tapping electrode. The disadvantage of the orthodromic technique, in comparison with the antidromic technique, is that at the first one, lower potentials (up to 3-5 μV) are recorded, which can be within the limits of the electromyograph noise. Therefore, an antidromic technique is considered preferable.

The most distal electrode (irritating with orthodromic and diverting - with antidromic technique) is better to be applied not to the back surface of the first finger. And in the area of the anatomical snuff box, about 3 cm below the styloid process, where the branch of the superficial branch of the radial nerve passes over the tendon of the long extensor of the thumb of the hand. In this case, the amplitude of the response is not only higher, but also subject to smaller individual oscillations. The same advantages have the imposition of the distal electrode not on the I finger, but on the interval between the I and II metatarsal bones. The average propagation velocities for sensitive fibers of the radial nerve in the area from the leaf electrodes to the lower forearms in the orthodromic and antidromic directions are 55-66 m / s. Despite individual fluctuations, the rate of propagation of excitation along symmetrical parts of the nerves of the limbs in individuals on both sides is approximately the same. Therefore, it is not difficult to detect a slowing of the rate of propagation of excitation along the fibers of the superficial branch of the radial nerve when it is unilaterally involved. The speed of propagation of excitation through sensitive fibers of the radial nerve is somewhat different in separate areas: from the spiral trough to the ulnar region -77 m / s, from the ulnar region to the middle of the forearm - 61.5 m / s, from the middle of the forearm to the wrist - 65 m / s , from the spiral trough to the middle of the forearm - 65.7 m / s, from the elbow to the wrist - 62.1 m / s, from the spiral trough to the wrist - 65.9 m / s. A significant slowdown in the rate of propagation of excitation through sensitive fibers of the radial nerve on its two upper segments will indicate a proximal level of neuropathy. Similarly, it is possible to detect a distal level of damage to the superficial branch.

[1], [2], [3], [4], [5], [6], [7]